WASHINGTON -- Buoyed by positive sales results and a more optimistic outlook among restaurant operators, the National Restaurant Association's Restaurant Performance Index (RPI) rose above 100 in March. The RPI – a monthly composite index that tracks the health of and outlook for the U.S. restaurant industry – stood at 100.6 in March, up 0.7 percent from February's level of 99.9. March represented the second time in the last three months that the RPI stood above 100, which signifies expansion in